The prior art includes a number of devices that rely on fluid oscillation effects to create pulsating fluid flow. Generally, these devices connect to a source of fluid flow, provide a mechanism for oscillating the fluid flow between two different locations within the device and emit fluid pulses downstream of the source of fluid flow. These devices require no moving parts to generate the oscillations and have been used in various applications for which pulsating fluid flow is desired, such as massaging showerheads, flowmeters, and windshield-wiper-fluid-supply units.
A typical prior art apparatus for creating pulsating fluid flow includes body 10 with a nozzle 20 that attaches to a fluid source 30, as shown in FIG. 1. The nozzle 20 expels the fluid as a jet into a chamber 40 toward a flow splitter 50. This flow splitter 50 traditionally assumes a triangular or trapezoidal shape, with a narrow leading edge directly in the path of the jet. The sides of flow splitter 50 form the inner walls of two fluid pathways 60 and 60′ that initially diverge and then become parallel as they leave apparatus. The body 10 forms the outer walls of the two fluid pathways 60 and 60′, as well as at least two feedback passages 70 and 70′ leading from the fluid pathways back into the chamber. Each feedback passage 70 or 70′ will be disposed along one of the fluid pathways, 60 or 60′, respectively.
The jet will cling to one side of chamber 40 due to a phenomenon called the Coanda effect, explained in more detail later in this disclosure. Thus, the fluid will flow through one of the two fluid pathways 60 or 60′ at a time. Flow splitter 50 also helps guide the flow into either fluid pathway 60 or fluid pathway 60′. As the fluid flows through one fluid pathway such as fluid pathway 60, feedback passage 70 will divert a portion of the fluid and return it to chamber 40. The fluid will then disturb the fluid flow along the side of chamber 40 closest to fluid pathway 60. This disturbance will cause the fluid flow to switch to the side of the chamber closest to fluid pathway 60′. Fluid will thus leave from fluid pathway 60′, rather than from fluid pathway 60. As a result, the apparatus for creating pulsating fluid flow will emit pulses of fluid in succession from the two fluid pathways 60 and 60′, with only one fluid pathway 60 or 60′ ejecting fluid at a given time.
Generally, prior art apparatuses for creating pulsating fluid flow are manufactured from two rectangular blocks of a material suitable for the particular application. For example, if the apparatus for creating pulsating fluid flow will be used in a well bore, stainless steel blocks may be appropriate. A path for fluid flow is machined into the largest flat surface of one of the rectangular blocks. The two blocks are then joined together and the entire apparatus is lathed into a generally cylindrical form. This method of manufacture is labor-intensive and time-consuming.
Some applications for apparatuses for creating pulsating fluid flow require sharper fluid pulses than others. For example, apparatuses for creating pulsating fluid flow may be used to clean fluid flowlines or well bores. The apparatus for creating pulsating fluid flow is joined to a source of cleaning fluid and then is inserted into the flowline or well bore. Pulsating fluid flow has been found to be superior to steady fluid flow for cleaning surfaces such as the interior of a fluid flowline or well bore. Moreover, sharp fluid pulses dislodge buildup and debris from these surfaces better than less-defined fluid pulses because sharply defined pressure pulses have a higher frequency content. Prior art apparatuses, however, may not provide the pulse definition cleaning applications require. In addition, because prior art apparatuses emit fluid parallel to the nozzle, they do not always effectively clean areas located alongside the apparatus. For example, a prior art apparatus used downhole will not remove matter caked on the well bore because it will eject fluid down the center of the well bore, not at the sides.
Prior art apparatuses for creating pulsating fluid flow often exhibit erratic, weak or even no oscillation when used in submerged environments such as fluid flowlines or well bores. Prior art apparatuses generally rely on atmospheric air to boost the fluid oscillations. These apparatuses accordingly allow air to enter the path of the fluid. These apparatuses fail to provide reliable, robust fluid pulses in environments where air is unavailable, such as in fluid flowlines or well bores.